Review fixes for SEP-2575 client conformance scenario#1
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SEP-2575 makes each request self-contained: "Servers MUST NOT rely on prior requests over the same connection to establish context (e.g., capabilities, protocol version, client identity)." Nothing forbids a client from sending a different protocolVersion on a subsequent request, so this check would FAIL a spec-compliant client. Removes the check, the flippingVersionClient negative test, and the redundant second tools/list call in the example.
- client-calls-discover: spec says clients "MAY call it" — MAY-level behavior gets no check row. Handler still responds so a client that does call discover proceeds normally. - client-cancels-by-notification: spec scopes notifications/cancelled to stdio. For Streamable HTTP it states "No notifications/cancelled message is required or expected." Unreachable from a compliant HTTP client. - client-cancels-by-closing-stream: the normative sentence is "Closing the SSE response stream MUST be treated by the server as cancellation" — a server obligation (sep-2575-http-server-disconnect-is-cancel in #271), not a client one. The req-on-close handler also fires on any disconnect, so it could only ever emit SUCCESS. Removes the long_running_task plumbing and example flow that existed only to exercise these.
Spec: "Every POST request to the MCP endpoint MUST include an MCP-Protocol-Version header" and "Every client request MUST include … _meta". Both are unconditional, but the previous code: - guarded the header check behind `if (currentVersion)` (so a request with no _meta got no header check), and - ran the _meta check after the server/discover early-return (so the example discover call, which sent neither header nor _meta, passed). Now both checks fire on every POST including server/discover, and the header requirement is split into the two distinct spec sentences: - client-sends-version-header (presence) - client-version-header-matches-meta (header == _meta.protocolVersion) Adds a mismatchedHeaderClient negative test for the new check and fixes the example to send header + _meta on discover.
Aligns with the traceability YAML in #273 so the coverage tooling can match check rows automatically. Also pins the badClient negative test to both slugs it now fails (it sends neither header nor _meta).
#265 replaced specVersions: SpecVersion[] with source: ScenarioSource on the Scenario interface. This branch predates that, so it would not type-check after merging main.
Post-SEP-2575 there is no stateful mode to contrast with, so "stateless" describes the SEP rather than what this scenario checks. The checks here are the per-request _meta and MCP-Protocol-Version header obligations, which the spec groups under "Request Metadata".
Carries the requirement-traceability YAML from #273 so the scenario PR is self-contained. The 6 stdio-transport rows are moved to excluded: with a pointer to #258 (stdio client harness tracking issue) — the conformance client harness is HTTP-only today, so these are not reachable until #258 lands. The 3 prior excluded: rows from #273 are kept as-is.
This was referenced May 15, 2026
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Thanks for the PR! Updated modelcontextprotocol#270 with these changes and others highlighted. Let me know your thoughts! :) |
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Stacked on modelcontextprotocol#270 — one commit per finding from the review. Merging this into your branch will pull all of them into modelcontextprotocol#270.
client-consistent-version— spec lets clients varyprotocolVersionper requestclient-cancels-by-notification(stdio-only),client-cancels-by-closing-stream(server-side req),client-calls-discover(MAY)_metachecks on every POST incl.server/discover; split header presence vs match; fix example discover callsep-2575-*to match the traceability YAML; fillspecReferencesURLsspecVersions→source: { introducedIn }(rebase prep for modelcontextprotocol#265)stateless→request-metadatasrc/seps/sep-2575.yaml(carries modelcontextprotocol#273; stdio rows excluded → modelcontextprotocol#258)After this,
--scenario request-metadataruns green againsteverything-client(6/6) and the 3 negative tests pass. Still uncovered (follow-up welcome):sep-2575-client-declares-{elicitation,roots,sampling}-capabilityandsep-2575-client-retry-supported-version.Note: 159c026 targets the post-modelcontextprotocol#265
Scenariointerface, so a rebase onto currentmainis needed before modelcontextprotocol#270's CI will type-check.